The present invention relates generally to high-capacity digital communications systems, and more specifically to a digital communications system and method of transporting 10 Gbit/s Ethernet LAN data packets over an optical transport network.
In recent years, Optical Transport Networks (OTN networks) have been increasingly employed for transporting 10 Gbit/s Ethernet (GbE) LAN (10 Gbase-R) data packets between Ethernet client devices. A conventional technique of transporting 10 GbE LAN data packets from a source device to a destination device over an OTN network includes terminating the Ethernet LAN physical layer, extracting the 10 GbE LAN packets, encapsulating the packets using the Generic Framing Procedure (GFP), and mapping the GFP encapsulated packets to the payload of one or more ODUk frames for subsequent transport over the network.
One drawback of the above-described technique of transporting 10 GbE LAN packets over an OTN network is that the Ethernet signal generally cannot be transported in the ODUk payload as a Continuous Bit Rate (CBR) signal. This is because the data rate of the 10 GbE LAN signal is typically higher than the payload rate of the ODUk frame. For example, the data rate of the 10 GbE LAN signal is equal to 10.0000±100 ppm Gbit/s, and the data rate of an OPU2 payload is equal to 9.9953±20 ppm Gbit/s. For this reason, flow control is usually employed to assure that no packets are lost while transporting the 10 GbE LAN signal between the source and destination devices on the network. However, requiring the use of flow control techniques precludes transporting the 10 GbE LAN packets over the OTN network in a manner that is transparent to the destination device(s).
Another known technique of transporting 10 GbE LAN packets over an OTN network includes removing the preamble from each 10 GbE LAN packet, GFP encapsulating the packets, and mapping the GFP encapsulated packets to the payload of ODUk frames. This technique typically comprises the removal of the 8-byte preamble from each Ethernet packet, and the addition of an 8-byte GFP header to the packet. However, some client applications employ the preamble when mapping client application data to the Ethernet packets. Removing the preamble from each Ethernet packet may therefore lead to the loss of client data. Because this second technique also typically results in a 10 GbE LAN data rate that is higher than the ODUk payload rate, flow control is normally required to avoid any further data loss, thereby making it difficult to transport the 10 GbE LAN signal in a transparent manner.
It would therefore be desirable to have an improved digital communications system and method of transporting 10 GbE LAN data packets over an OTN network. Such a digital communications system would avoid the drawbacks of the above-described conventional communications techniques.